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Influenza Vaccine Composition Recommendation for the 1989-90 Season

During the 1988-89 influenza season, influenza type B has predominated in the United States but has cocirculated with type A(H1N1) and A(H3N2). Elsewhere in the Northern Hemisphere, type A influenza has generally predominated, with both influenza A(H1N1) and A(H3N2) cocirculating.

Antigenic analysis of type A(H1N1) viruses from outbreaks indicates that most strains are closely related to the U.S. vaccine strain, A/Taiwan/1/86. The antibody induced by this vaccine component reacts well with the recently circulating type A(H1N1) viruses.

As in last season, type A(H3N2) viruses continue to be heterogeneous. Some isolates resemble the current vaccine strain A/Sichuan/2/87, but most are better inhibited by antiserum to the A/Shanghai/11/87 reference virus (Table 1). In addition, patients vaccinated with A/Sichuan/2/87 vaccine consistently had lower antibody responses to the A/Shanghai/11/87 strain (Table 2) than to the vaccine strain.

Most influenza B strains isolated this season, particularly in the United States, are similar to the current vaccine component, B/Victoria/2/87. However, a new variant was identified in Asia; B/Yamagata/16/88 is an example of the variant (Table 3). This strain was first seen in the People's Republic of China in August 1987 and circulated in Japan, Hong Kong, Singapore, Taiwan, and Thailand from February 1988 to January 1989. The antibody induced by the current B/Victoria/2/87 vaccine component is poorly reactive with the B/Yamagata/16/88 strain (Table 4).

Based on these and other data, the World Health Organization (WHO) has recommended that the trivalent influenza vaccine for use in the 1989-90 season contain the following components: type A(H3N2), A/Shanghai/11/87-like antigen, and type B/Yamagata/16/88-like antigen and retain the type A(H1N1) component of the current vaccine. This decision has been ratified by the Food and Drug Administration's Vaccine Advisory Panel. Reported by: P Gross, MD, Hackensack Medical Center, Hackensack, New Jersey. P Palmer, K Edwards, MD, Vanderbilt Univ, Nashville, Tennessee. F Ruben, MD, Univ of Pittsburgh, Pennsylvania. Influenza Research Center, Baylor College of Medicine, Houston, Texas. G Schild, PhD, National Institute of Biological Standards and Control, London, United Kingdom. National Influenza Centers, Microbiology and Immunology Support Svcs, World Health Organization, Geneva. Div of Virology, Office of Biologics, Food and Drug Administration. Participating state and territorial epidemiologists and state laboratory directors. WHO Collaborating Center for Influenza, Influenza Br and Epidemiology Office, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Influenza type A viruses are classified into subtypes on the basis of two antigens: hemagglutinin (H) and neuraminidase (N). Three subtypes of hemagglutinin (H1, H2, H3) and two subtypes of neuraminidase (N1, N2) are recognized among influenza A viruses that have caused widespread human disease. Immunity to these antigens, especially the hemagglutinin, reduces the likelihood of infection and the severity of disease if infection occurs. However, over time there may be enough antigenic variation (antigenic drift) within the same subtype that infection or vaccination with one strain may not induce immunity to distantly related strains of the same subtype. Antigenic variation occurs with influenza B viruses, although no subtypes are known to exist. For these reasons, major epidemics of respiratory disease caused by new variants of influenza continue to occur. The antigenic characteristics of current strains provide the basis for selecting virus strains included in each year's vaccine.

The manufacturing, quality control, and distribution process involved in producing about 30 million doses of influenza vaccine in the United States require many months to complete. Therefore, the decisions on which strains to include in the vaccine formulation for the 1989-90 influenza season must be completed by late March to early April of 1989. Specific recommendations by the Immunization Practices Advisory Committee will be available later this spring.

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